The proposed research is concerned with the following three problems: (1) short-term memory (STM) for item, spatial, and temporal information for visually-presented verbal stimuli (letters) and patterns (matrix patterns); (2) comparison processes between items in perception and STM for verbal vs. patterned stimuli which are either temporally or spatially distinguished; (3) the form of storage in long-term memory for pictorial as opposed to verbal material. Problems (1) and (2) will be studied by a two-choice classification reaction time task. For (1) stimuli will be presented in either a temporal or spatial array, and memory for an item in a particular location will be probed by presenting an item in that location which is either identical to or different from the original item. For (2) a paradigm developed by Townsend (1972) will be used to distinguish a general class of parallel from a general class of serial exponential models, based on differences among means. Subjects will be encouraged to use either serial or parallel comparison processes by varying the nature of the stimuli, and varying whether they are presented in spatial or temporal locations. Problem (3) will be studied by using a recognition memory paradigm in which one of two forms of a stimulus -- a picture or its corresponding word -- are presented to be memorized, and recognition is tested using intrusion or noise items which correspond in identity but not in form to old items.